In the prior art, the technical teachings of documents U.S. Pat. Nos. 5,984,382A, 6,343,815B1, 6,382,690B1 and 7,131,672B2 are known to disclose hook latches.
Typically, such latches can either be connected to the fixed structure of the apparatus and capable of fastening and maintaining its mobile structure, or be connected to its mobile structure and capable of fastening its fixed structure to attach said structure.
FIG. 1 represents, in a schematic manner, a cross-section of a hook latch 11 according to one embodiment from the prior art in its environment and in a locked non-flush position. In this example, the latch 11 is assembled onto a mobile structure 13 of an aircraft so as to fasten a keeper 15 positioned on a fixed structure 17. For two distinct surfaces, a flush position implies a position in which the former two surfaces form a single surface.
The latch 11 comprises a handle 19 and a fastener known as an adapter 21, in which a hook 23 is assembled via a fitting part such as a nut 25. The nut 25 adjusts the sinking of the hook 23 within a recess 27 of the adapter 21. The handle 19 and the adapter 21 are assembled via a rivet 29 located at one end of the latch 11 opposite the hook 23. The rivet 29 extends along an axis 31 of rotation of the adapter 21 in relation to the handle 19. A locking element such as a trigger 33 secures the handle 19 in its closed position.
The mobile structure 13 has a second pivot connection axis 35 around which the latch 11 assembly is guided in rotation. In this example, the second pivot connection axis 35 is substantially parallel to the first axis 31 and is materialised by a rod 37 fixed in relation to the mobile structure 13 and passing through a strut 39 connected to the handle 19.
The hook 23 has a shape capable of fastening the keeper 15 extending along a third axis 41 parallel to the first two axes 31 and 35.
The adapter 21 has an overall cylindrical section 43 in which the recess 27 is fitted, which is partially tapped. A first pin 45 passes through the cylindrical section 43, thus fulfilling the function of locking the hook 23 in rotation in relation to the adapter 21. In this example, the pin 45 extends along an axis perpendicular to a rod 49 of the hook 23.
The hook 23 extends into the threaded rod 49, said rod being capable of being screwed, via this threading and the adjustment nut 25, within the recess 27 of the adapter 21. For this purpose, the nut 25 is threaded and tapped.
The handle 19 has an upper surface 51, in theory intended to be positioned flush with an aerodynamic surface 53 of the apparatus so as not to reduce the overall aerodynamics of the apparatus. However, due to the various manufacturing and assembly tolerances, it appears that the upper surface 51 of the latch 11 is often, as shown in this example, in a non-flush position, i.e. the ends of the handle 19 are not aligned with the aerodynamic surface 53 of the apparatus, which represents a considerable reduction in aerodynamics, an increase in aerodynamic drag and therefore a significant increase in the amount of fuel consumed by the apparatus.
For mobile structures with high aerodynamic stresses, for example aircraft radomes, i.e. the domes located at the front end of the aircraft generally protecting a radar antenna, the effect of the flushness of the latches with the upper surface is vital. This type of latch, although frequently used, therefore creates a major technical problem for one of ordinary skill in the art. In the prior art, in order to try to improve the positioning of the upper surface of hook latches, the only solution considered by one of ordinary skill in the art consists in adjusting, on the fixed structure of the apparatus and via a complex adjusting device, the fastening point for the hook. However, this solution requires the latch to be unlocked so as to separate the mobile elements from the structure and thus access the adjustment system for the fastening point. This leads to a non-negligible loss of time, and therefore a lengthy downtime for the apparatus. Moreover, this requires the implementation of human means and the use of specific tooling.